how aswan bonus coins work.

Concerning what you get on bonus coins, it does follow a certain "formula." However, it isn't consistent with every character for instance, I got 6 silvers on my 7th run on 1 character and the other character I had online (yes, leeching myself) received 7 silvers. How could I receive more coins on a char that just afked there than a char that was doing all the killing? I can only guess that even if the midway through the formula it might not be 100% the same, the ending is always the same (at least for me anyways). I always end up with 15, 16, 17 as the last 3 bonuses on all chars.